Generally, an “Open Access” service model refers to a network architecture where multiple Service Providers (“SPs”) share the common data-link layer that typically belongs to the network owner, to provide voice, video, and data services. A typical example of an “Open Access” service model is various Internet Service Providers (“ISPs”) that compete to provide Internet access to residents and businesses over a wired network. In Passive Optical Networks (“PONs”), passive optical components, e.g., fibers, splitters and couplers, are provided to guide traffic between a Central Office (“CO”) and termination points at the customer premises. The passive optical components do not have power or processing requirements thereby lowering overall maintenance costs.
FIG. 1 shows a typical PON 100 for a point-to-point connection architecture. As shown in FIG. 1, each customer (1 . . . n) at remote sites 120 is connected to a respective pair of transmitters and receivers (1 . . . n) at central office 110 by a dedicated pair of optical fibers. As shown in FIG. 1, receiver Rx 103 at customer 1 is connected to transmitter Tx 101 at Central Office 110 using a fiber 105, transmitter Tx 113 at customer 1 is connected to receiver Rx 111 at CO 110 using a fiber 106, receiver Rx 104 at customer n is connected to transmitter Tx 102 at CO 110 by a fiber 107, transmitter Tx 114 at customer n is connected to receiver Rx 112 at CO 110 by fiber 108. As shown in FIG. 1, such a point-to-point connectivity where each receiver and transmitter at remote sites 120 has an individual fiber connection to a transmitter and receiver at the CO requires a lot of fibers and therefore is expensive.
FIG. 2 shows a typical Time Domain Mulitplexed (“TDM”) PON architecture. As shown in FIG. 2, CO 210 has an Optical Line Termination (“OLT”) unit 201 that consists of a single transmitter Tx and receiver Rx pair. OLT unit 201 is connected to customers (1 . . . n) at remote sites 220 through a feeder fiber 204, a power splitter 206, and individual distribution fibers (1 . . . n). As shown in FIG. 2, feeder fiber 204 transmits optical signals from OLT unit 201 at CO 210 to optical power splitter 206 located at a remote location. The optical signals are distributed from optical power splitter 206 to optical network units (“ONUs”) (1 . . . n) located at customer premises through distribution fibers (1 . . . n). As shown in FIG. 2, ONU 202 consisting of one receiver Rx and transmitter Tx pair is connected to power splitter by fiber 205, and ONU 203 consisting of another receiver Rx and transmitter Tx pair is connected to power splitter by fiber 207. In TDM PON architecture, the same bandwidth is shared between multiple ONUs, and dedicated transmission time slots are granted to each individual ONU, to avoid data collision. As shown in FIG. 2, all remote users share a common data stream over feeder fiber 204. Therefore, one user can not have more bandwidth without decreasing the bandwidth of other users.
Furthermore, all remote users share a single transmitter/receiver pair of OLT unit 201 at CO 210, as shown in FIG. 2. The single transmitter/receiver pair of OLT unit 201 at the CO is difficult to share between multiple service providers. As such, TDM-PONs do not support Open Access service model.